Metal Melter

[Onoff]

@Kram the investment powder I gave you is Pioneer Smoothcast Classic from H Walsh at Biggin Hill. Think I paid £10/5kg and gave you half.

Looking at their site they also do this one. Says it's great for brass and designed specifically for 3D printed parts.

A bit spendy at £40/25kg unless it actually works!

Protocast Investment Powder Casting Resin Pieces 3d / CAD 22.5KG - TC0459

Investment Powder for Casting

www.hswalsh.com

Short term you can have the other 2.5kg of the classic stuff I have here.

 

[DAPPH]

Plan to try the former either today or this week.

@DAPPH How much of that is from experience?

I have some borax but it would eat the cuicibles quicker, so I dont use it. I might try citric cleaning the nuts and graphite powder or a carbon source as a cover. However with a huge surface area of nuts, losing 10% is acceptae I think, should be much less when remelting solid bits.

The 3d print will need under 170g of brass. The problem was my carved sand runners leaked and used more than I expected. A previous one was 350g.. A traditional plaster pouring tree would use less brass, but double the plaster - dont have all that much left! 2 or 3 more attemps.


Turbulence is not desired. Slow is much better. With the correct excess of brass there will be plenty of head to get the air out when a porus medium is used. Its not an extreme detailed object like a grasshopper*


Sprues are for filling, there is only one and it should be a very specific size.
Vents, yes they can be many, shouldnt be needed with porus plaster. 1/4" is way too big.

I may change things and try using the vacuum chamber for the next pour.


*

About 99% but it was 54 years ago . I kept up interest , casting an aluminum support stay for an ancient coronet multi purpose saw milling station. Cast it in POP from a super cgli=ued up broken support some 5x6 " triangular form . plus numerous other small alu castings . The biggest thing was getting the cast bone dry , 60 hrs in a 50 oC electric oven seemed to work well . Preheating the cast to 200 oC for an hour to warm it up for pouring into .

Used our multifuel stove / log burner as the fire because I could get it almost white hot if I set the dampers right and opened the patio doors .

 

[Kram]

Im unsure how well plaster keeps, had a bag of building plaster go off in a sealed bag. A big bag might be wasted. Theres enough for the next couple tries.
I'll get a bag of building plaster which will be ok for the pouring basin/sprues half which I think I'll try next, see how it compares. The only difference seems to be the proper stuff is 50%+ of very fine sand.

If your going past the shop I'll order a 5kg bag and get you to collect, but they are showing out of stock at the moment.

 

[Onoff]

I'm plucking up the courage to cut the top off a gas cylinder to make a furnace like @Kram . Yep, I know to fill with water. The cut off top will form the hinged lid.

I'll be cutting with a 1mm slitting disc and am confident of cutting a nice, neat line (I have a plan). Is there any merit in welding the hinge on first, then cutting? That way the two cut pieces will align the best they can.

https://flic.kr/p/2nmtULZ

https://flic.kr/p/2nqe9wc

 

[Kram]

I did it after, it'll just get in the way. Do you have a proper hinge? I used some 3mm sheet, 16mm holes drilled and a peice of mild bar as the pivot, quite happy with the result.

For cutting, sabre saw is ideal I think. Very easy to get a nice straight cut and a lower chance of going bang.

 

[DAPPH]

@ Onoff
Once the thing is safely emptied, the valve removed & it's been well flushed out & de-fumed set yourself up for safe cutting where the cylinder can't roll away or mess you up .

I did the now valveless cylinder with it upside down in a simple frame, with my power washer blasting away up the hole for two sessions of 10 min each whilst using the wide-angle rotating spray at 140 bar. Left it to drain fully & sweeten up for two days in this upside-down position ...not a trace of the signature odour of a propane gas cylinder.

Cutting .
Perhaps bolt your angle grinder securely to a vertical stand via the bolt on side handle thread at the height you want to cut at.
Then anchor the stand to the ground or a bench leg, get the grinder going withthe trigger /slider fixed to the on position. Then slowly introduce the cylinder to the locked-on angle grinder fitted with a slitting disc cutter and gently rotate the cylinder ( I used the thin swivel seat pad out of my Motability car) to stand the cylinder on & a router cut disc of MDF to rotate the cylinder on.
I got a lovely clean cut of equal height all-round the cylinder, far better than I would if I'd freehand cut to a pencil line as everything was fixed in place.

I've done this for cutting all manner of metal or plastic containers where I wanted the top off or to have them cut to half height etc. & have a clean edge that just needed the sharpness removing with a file , scraper or flap disc etc .

 

[Onoff]

I did it after, it'll just get in the way. Do you have a proper hinge? I used some 3mm sheet, 16mm holes drilled and a peice of mild bar as the pivot, quite happy with the result.

For cutting, sabre saw is ideal I think. Very easy to get a nice straight cut and a lower chance of going bang.

I don't have a hinge, was just going to fab something like yours.

@DAPPH yes was going to fix the grinder then gently rotate the cylinder against it to at least mark a cut line.

 

[Onoff]

Discussing with @Kram all things brassy and poury...

The thinking is now to maybe cast the horse brass without the lettering and CNC engrave or acid etch those later. First job is getting the horse brass of course but the lack of letters should make the brass flow easier.

Thus I had my lad print a PVA mould without letters.

Next heated the proper casting wax and poured into the mould:

It was a tad over filled so I stuck it under the grill and then dragged a lolly stick across the top:

Left me with this which I bunged outside the back door to rapidly cool down!

Tbh it's possibly now a tad under filled as I forgot wax shrinks when it cools!

Staeted soaking in body temperature water to soak off the PVA:

Then decided to try an aquarium pump to speed the removal of the PVA:

 

[Onoff]

Wasn't happy with the shrinkage so added more wax:

https://flic.kr/p/2o5UDds

Back under the grill to level out then outside to harden off. Not the best method as the molten layer can shift. I think something similar can happen when floating glass, it's called "roller wave".

The aquarium pump certainly seems to help dissolve the PVA:

https://flic.kr/p/2o5PMtE

 

[Kram]

the lack of letters should make the brass flow easier.

That problem should be fixed when I do the next one with text. The last one I messed up the mould and, didnt have enough brass melted...
I'd quite like to see it with the text anyway, the successfull letters on the first one looked good.

The reason I see for doing it without text, is if it were in two parts, the outer ring is simple enough to sand cast, and I have already cast a good inner-cow, this would make it really easy. The small induction cruicible is big enough for that, too.
Then silver solder them together, and you'd never know it wasnt cast as one. But you dont like that idea fair enough


Just seen this,

Today Im stuck with decorating, but I might get to lathe later and then assemble the induction coil..

 

[Onoff]

The latest, plain wax model, sans lettering. Probably the best yet for detail around the eyes and snout. Managed to soak the PVA off within about 12 hours. The photos aren't particularly flattering mind.

 

[Kram]

Getting the next print ready. The rest have a bigger ring and theres no way it will fit the furnace for burn out, so this one will be two parts. However Im not sure I need furnace temperatures, so I will try making a bigger flask for next one.

Added a thin layer of candle wax to allow more brass flow on the text.

Plaster went ok except I couldnt get chamber to seal properly after pouring, only 1/4 vacuum.
Used 650g plaster to 260ml water - for next time, its about perfect for this size.

 

[Onoff]

I've the other 2.5kg of powder here I'll bring down when I see you. It's going to be hilarious if I get stopped by the Police...

 

[Onoff]

Could you cast with the wax / PLA model at a 45 degree or more angle. Thus you're almost tipping molten metal into an open "bucket"? Thinking you wouldn't need such a large dia furnace. Guess though you would need lots more plaster?

 

[Kram]

I did burnout in the kitchen oven. Some of the letters were not great either from plastering or, I have the lid a gentle wiggle which may have broke them. Flame to finish burnout didnt help.

Note the dent.. I dropped it. Still useable.

Assembled the big coil but it wasnt great, too long? Couldnt get more than 13A out of it, so enlarged the original coil, and that gave ~32A.

Not quite enough transfer, it was getting to 750-850c I think. Not quite enough to melt brass and quite a way off pouring.
A smaller coil and air gap would help, but cant let it touch and short.
The coils fibreglass sleeve insulation is only good for a few hundred celcius.

Then I chucked a 75mm lump of steel in the coil, easily went above 52A, 2500w+..

While induction heats the pure graphite cruicibles, it doesnt seem to touch the graphite/sillicon carbide clay type, meter didnt move.

 

[Kram]

Ordered one of these hotplates, should be good for i initial burn outs and keeping the plaster hot during a melt. The 220-240v thin wires dangling out is going to be questionable, I think I'll make up a alu surround to house a small fused IEC kettle socket.

https://www.amazon.co.uk/dp/B09656V212

Should arrive in an hour or so..

 

[Onoff]

Lad up the pub lent me a book:

 

[oldbikedavey]

On the lost wax process, I did a fair amount of research, acquisition, and practice.
For me, it was a rabbit - hole, and I just left it alone thereafter.
Now, my foundry operations, such as they are, involve propane fired furnaces, oil sand, and ramming with an air chisel equipped with a flat foot.
Plate type patterns are nice to mould with, and differing moulding box sizes keep irrelevant sand volumes as low as possible.

 

[Onoff]

On the lost wax process, I did a fair amount of research, acquisition, and practice.
For me, it was a rabbit - hole, and I just left it alone thereafter.
Now, my foundry operations, such as they are, involve propane fired furnaces, oil sand, and ramming with an air chisel equipped with a flat foot.
Plate type patterns are nice to mould with, and differing moulding box sizes keep irrelevant sand volumes as low as possible.

Do you reckon this would be suitable for casting in brass using the oil sand technique?

https://flic.kr/p/2o6Anxw

What sand & oil btw?

 

[oldbikedavey]

Do you reckon this would be suitable for casting in brass using the oil sand technique?

https://flic.kr/p/2o6Anxw

What sand & oil btw?

Not remotely ! But, then again, I tend to cast in aluminium alloys or zinc. Brass or bronze need a heck of a lot more heat to be pourable, and are an all round PITA....
Using petrobond, but a silica sand/sawdust/linseed oil mix for cores. Bit of pilchard oil in the stuff makes it a touch less tenacious...